In my humble experience sometimes a bit too much heating happens to make the bore never shrink back. A friend of mine uses liquid Nitrogen when for example pressing new valve leads (sorry not sure it's the correct English term) into a cylinder head.

Big problem is the coefficient of friction, anywere between 0.18 and 0.3 is seen in practice, and if you were disassembling it can go higher.

Her's several answers::

Then you need an equation called Lame's equation for press fits.

http://www.tribology...lators/e3_8.htm/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////It's a tricky piece of maths to derive that. If the geometry of the outer is complex you'll need FEA or tests.

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////If that calculator is no good (I haven't checked it lately) then any good machinist's handbook should have a table. ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////Here's a formula I grabbed off the web, but I have been told it is incomplete.

Alternatively desertfox looked up the equations, so you can roll your own:

where x = total interference Dc=dia of shaft Di = inner dia of shaft(this is zero for solid shaft) Do= outside dia of collar Uo=poissons ratio for outer member Ui=poissons ratio for inner member Eo=modulus of elasticity for outer member Ei=modulus of elasticity for inner member

Why do you want to calculate the force needed?
I would have thought the usual procedure would be to use a puller, if that didn't work, then a press, then heat, liquid N2, bad language etc. Doesn't seem to be much point in calculating the force needed.

Why do you want to calculate the force needed? I would have thought the usual procedure would be to use a puller, if that didn't work, then a press, then heat, liquid N2, bad language etc. Doesn't seem to be much point in calculating the force needed.

When you are they guy that are supposed to design the puller or the press it is.

Matts,
If it theoretically is going to take 76 tonnes to dismantle these components then I think a press is going to be the only way.

If you have seen a 100 tonne workshop press then you will know how robustly they are built to withstand the maximum operating force.

That said, any puller you might want to fabricate is going to resemble the press in order to withstand the forces involved.

I would be trotting over to your other division and ask them nicely about using their press. (Here in Australia the custom is to offer beer as an inducement. The usual currency is a "slab" or carton)

As mentioned some heat would be useful . In addition when parts like this are loaded in a press a shock load introduced via a hammer at a suitable spot can often be enough to get things to start moving.

Caution ! When pressing components with loads of this magnitude use all safety protection available. Loads like this can be very destructive. Things like bearing races can shatter causing shrapnel to fly about your ears. Take care.

I don't want to critisize anybody's engineering as I am not an engineer but if it for a train where such high forces are involved is an interference fit the best overall solution?

I see Greg has quoted co-efficients of friction in a 2:1 ratio and there is ( maybe) a presumption that the interference fit will be consistent over 108mm on a what is , I assume, a large bore item.

Again , I am not qualifed to give opinions here but how safety critical is the joint? I know train tyres ( the actual steel band touching the track) are mounted with heat and cold in an interference fit but that is strict radial load and IIRC safety locks are ofen fitted as there is a history of rail tyres working loose with nasty results

Marier's point is good, there is no particular reason why you should use parallel shafts and bores in an interference fit, but I think experience suggests they work well, and things might wobble if you had a barrel shaped shaft, or burst if you had a barrel shaped bore. I suppose you might think about tapers, but that gives me the creeps (literally, the wheel would tend to wiggle off the shaft).

Marier's point is good, there is no particular reason why you should use parallel shafts and bores in an interference fit, but I think experience suggests they work well, and things might wobble if you had a barrel shaped shaft, or burst if you had a barrel shaped bore. I suppose you might think about tapers, but that gives me the creeps (literally, the wheel would tend to wiggle off the shaft).

Dunno what a barrel shaped bore is? you mean the part got a oval outer shape? it does..

Do not know anything about tapered pressfits. But i think they get used on either boat propellers or electric water turbines. guessing with the cone towards the jet then and it would be fine.

Edit: 13.02.2012

Its a parallel shaft and bore.

"But i think they get used on either boat propellers or electric water turbines."Thats correct. I saw some a few years back. Rather big taper too. And they had a oil channel for the dismantling.

Sounds doable to me. we just freeze the shaft and heat the bore. Add a press as well and we can perhaps reduce the temperature needed somewhat.

Liquid nitrogen and a press works well - I have used this method a couple of times. I have seen railway-type wheels (from a travelling crane) fitted to a axle by heating the wheel with oxy-acetylene torches. I don't know what temp was used - but it was very, very hot - maybe something over 300 degrees C. From memory, I think the wheel just dropped on to the axle under its own weight.

Most engineers and so on go crazy if you suggest heating something beond 120degrees celsius. while there is no structural chance going on below 200Celsius. And personally i don`t think its a Mega issue going beond that either... anehealing does need a long long time to take out the hardness. so a in comparison sudden heating and air cooling should not be a big issue. But im not metallurist. Few of those here btw.

one part is that the manufacturer of these parts does not sell them individually.

Second is that there will be tearing if you dismantle the parts. So neither part would be reusable. Supposedly.

And working in norway means its highly likely to be cheaper to buy the parts premounted from Germany.

its supposedly 6 on each train set. 36 sets in norway, price is around 5000-7000$ so far pr part if the ratio is 6.5:1 Kroner/Dollar
Thats a lot of money so its not unlikely the train company decides to alter the design to spline if possible.